Piston displacement of one cylinder

Aviation Mechanic General (AMG) practice question 14 of 25 on Mathematics. ACS element AM.I.H.K2 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA reciprocating engine has a cylinder bore of 5.5 inches and a stroke of 5.4 inches. Using 3.1416 for pi, what is the piston displacement of one cylinder?

AAbout 513.2 cubic inches
B128.29 cubic inches
C23.76 cubic inches

Show the answer and explanation

Correct answer: B. 128.29 cubic inches

A — incorrect This uses the full 5.5-inch bore as the radius; the radius is the bore divided by 2.
B — correct v = π × (bore ÷ 2)² × stroke = 3.1416 × (2.75)² × 5.4 = 23.758 × 5.4 = 128.29 cubic inches.
C — incorrect This is only the cross-sectional area of the cylinder (π × r²); it must still be multiplied by the 5.4-inch stroke.

BACKGROUND

Piston displacement is the total volume swept by the pistons of a reciprocating engine in one revolution of the crankshaft. For one cylinder it is the volume of a cylinder: π × (bore ÷ 2)² × stroke, where the bore is the inside diameter and the stroke is the distance the piston travels. With a 5.5-inch bore and 5.4-inch stroke, the calculation is 3.1416 × (2.75)² × 5.4 = 128.29 cubic inches. Total engine displacement multiplies this by the number of cylinders, giving 1,026.32 cubic inches for eight cylinders.

STUDY TIP

Work it in two steps: find the circular area from half the bore, then multiply by the stroke and by the number of cylinders.

KEY POINTS

Piston displacement = π × (bore ÷ 2)² × stroke × number of cylinders.
Bore 5.5 in, stroke 5.4 in: 128.29 cu in per cylinder.
Eight cylinders: 8 × 128.29 = 1,026.32 cu in.

SOURCES

FAA-H-8083-30B ch03 "Cylinder" (piston displacement example)

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